1. Field of the Invention
The present invention concerns an optical memory device conducting at least one of optical information recording, reading and erasing.
2. Description of the Related Art
An optical memory device such as a compact disk can conduct at least one of optical information recording, reading and erasing. Basically, as shown in FIGS. 3 to 6, there are a single-face type optical memory device 19, 23 comprising a transparent substrate 20 and a light reflection layer 21 or comprising a transparent substrate 24 and a recording layer (optical memory layer 25), as well as a both-face optical memory device 27, 35 comprising two transparent substrates 28 and 32, a reflection layer 29, 31 put between them or comprising two transparent substrates 36, 40 and a recording layer 37, 39 put between them. Each of the reflection layers 21, 29, 31 is composed of a metal film by vapor deposition or sputtering having high reflectivity to a semiconductor laser light, while the recording layer 25, 37, 39 is constituted with a film prepared by vapor deposition, CVD, sputtering or coating of optical recording material such as an magneto-optical recording medium or an organic photosensitive material.
The single-face type optical memory devices 19, 23 have a coating layer 22 and coating layer 26 made, for example, of a UV-cured resin being overlaid on the reflection layer 21 and the recording layer
The both-face type optical memory devices 27, 35 have adhesive layers 30, 38 made, for example, of UV-ray cured resin and the two optical disks 33 and 34 and the two optical disks 41 and 42 being bonded together by means of the adhesive layers 30, 38 respectively.
As has been described above, in the single-face type optical memory devices 19, 23 constituted by disposing the coating layers 22, 26 on each one surface of the substrates 20, 24, the coating layers 22, 26 serve to protect the reflection layer 21 and the recording layer 25. Further, in the optical memory device 27, 35 constituted by stacking the two optical disks 33 and 34, and the two optical disks 41, 42, information can be recorded on both surfaces and rear face thereby having a merit of increasing the recording capacity by twice and a merit of protecting the reflection layers 29, 31 and the recording layers 37, 39 (refer, for example to NIKKEI ELECTRONICS p187-206. Vol. 8.17 (1981); ibid, p 105-120, Vol. 3. 28 (1983); OPTOELECTRONICS TECHNOLOGY 1986 "Optical Disk System, Published from Optical Industry and Technology Association (1986, 2,
By the way, in the conventional structures as described above, for example, in the manufacturing step for the optical memory device 19, it is necessary to form the reflection layer 21 on the transparent substrate 20 and, thereafter, to form the coating layer 22 further. Further, in the manufacturing step for the optical memory 35, for example, it is necessary to form the recording layer 37, 19 to the transparent substrate 36, 40 respectively and, thereafter, to form the adhesive layer 38 further. With these reasons, they involve a problem of reducing the productivity, which leads to increased cost.